Time-resolved in situ X-ray diffraction study of the liquid-phase reconstruction of Mg–Al–carbonate hydrotalcite-like compounds

✍ Scribed by Millange, Franck; Walton, Richard I.; O'Hare, Dermot

• Book ID: 120931014
• Publisher: Royal Society of Chemistry
• Year: 2000
• Tongue: English
• Weight: 184 KB
• Volume: 10
• Category: Article
• ISSN: 0959-9428
• DOI: 10.1039/B002827O

✦ Synopsis

The brucite-like Mg 2z /Al 3z layered double hydroxide (LDH) was synthesized by using the coprecipitation method and calcined at a variety of temperatures. The starting LDH and the calcination products (mixtures of binary oxides and spinels) were characterized by X-ray diffraction, IR spectroscopies and thermogravimetric analysis. These techniques allowed us to con®rm that the double hydroxide possesses a brucite-like structure in which cations are octahedrally arranged. At moderate temperatures, the calcination products have a MgO-like structure where Al ions are dissolved in the lattice to form a solid solution. Calcination at high temperatures (up to 1000 ³C) yields a mixture of well-crystallized phases corresponding to MgO and MgAl 2 O 4 (spinel). The reconstruction of layered double hydroxides from material calcined at 400 ³C has been studied in situ by time resolved energy dispersive X-ray diffraction (EDXRD). Kinetic data for the reaction have been determined and modelled using the Avrami±Erofe'ev nucleation±growth model, consistent with the process taking place by dissolution of the starting material and crystallisation of the LDH from the solution.